A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.

A tremor-like cortical myoclonus. The tremulous movements are in fact small, high-frequency myoclonic jerks, induced by posture or action. They can be mild, but can also be more incapacitating. When present in the lower limbs, these may lead to gait disorders and even drop attacks. These tremor-like movements during action can be mistaken for essential tremor or epileptic seizures.